1. Field of the Invention
The present invention relates to data communication links operating in a highly stressed environment, and more particularly to receivers operable in such links.
2. Description of the Prior Art
Data communications links sometimes are required to operate reliably in highly stressed environments, such as, for example, space vehicles and deployable probes employed in planetary exploration missions, communications satellites and other space vehicles providing communications links to ground stations and the like. The link may be disturbed by such phenomena as amplitude and phase scintillation, atmospheric absorption, wind gusts and turbulence, probe or spacecraft gain, oscillator drift, Doppler effect, and Doppler rate and noise variations. Receivers utilized in such highly stressed environments may be required to acquire and track data signals impressed with these disturbances as soon as possible in order that data demodulation may then occur.
The present invention relates to receivers operable in such highly stressed environments. Because such receivers are utilized in space missions which are not only very expensive, but may take several years to complete from vehicle launch to mission completion, the performance and reliability requirements may be extremely rigid. State-of-the-art acquisition and demodulation techniques and receivers are understood not to be capable of meeting these rigid performance and reliability criteria in a fully satisfactory manner.